The majority of systems for road traffic monitoring currently used employ, for traffic monitoring, information coming from sensors and video-cameras placed along the roads, from drivers through telephone signalling to radio broadcasting stations which deal with providing information about traffic and/or from road police.
For road traffic monitoring, systems are also used which use position information coming from vehicles equipped with receivers which are able to determine the vehicle position, such as, for example, Global Position System (GPS) receivers.
Moreover, in recent years, road traffic monitoring systems are also used which are able to use position data coming from communication systems of the cellular type. These systems have the advantage of not requiring additional infrastructures, such as sensors, video-cameras or GPS receivers assembled on vehicles. They anyway allow having capillary traffic estimations, namely it is possible to have traffic estimations wherever there is a cellular coverage.
For example, U.S. Pat. No. 6,577,946 discloses an intelligent data gathering and processing system coming from existing cellular telephone networks. The system utilizes real time cell phone position data for reconstructing concurrent traffic conditions.
The system builds and maintains in time a list of vehicles moving along all road sections at particular points, by tracking all in-vehicle cell phones within a given region.
At each moment, the system maintains a series of such lists. This allows the system to obtain accurate estimations of the total number of vehicles travelling on each specific road section, together with their direction of travel and average velocity. Based on these data, the system is able to 1) compute real-time traffic loads for various roads and road sections; 2) generate detailed lists of vehicle turns, real-time turning data for all relevant intersection; and 3) other traffic parameters. The system uses heuristic algorithms to distinguish between position data coming from cell phones placed on vehicles or from cell phones of other users.
U.S. Pat. No. 6,650,948 discloses a method for monitoring vehicular traffic flow in a road network of an area served by a mobile telecommunication device network having a call management system provided with a mobile telecommunications device positioning system providing positional data for active mobile telecommunications devices. The method comprises: capturing geographic positioning data for individual devices carried aboard vehicles and converting these into probability vectors representing the likelihood of the vehicles having arrived at any of the possible road components of the road network compatible with the captured geographic positional data. As the vehicle travels along, this process is repeated and new probability vectors constructed based on the probability of any of the available routes between the road component position associated with the new probability vector and the road component position associated with the immediately previous probability vector. The expected transit times Δtx for the available routes are computed and compared with actual transit times to provide delay factors for the available routes.
U.S. Pat. No. 6,490,519 discloses a traffic monitoring system including a traffic data collecting apparatus adapted to collect location information from a plurality of mobile communication device users and a traffic data filter adapted to analyse location information coming from the plurality of users and removing location information which do not deal with vehicle traffic.